The present invention relates to an electrolytic solution and a battery using it, and more particularly to an electrolytic solution effective for the case using an anode active material containing at least one of tin (Sn) and silicon (Si) as an element and a battery using it.
As electronic devices have been downsized, development of batteries having a high energy density has been demanded. As a battery meeting such a demand, there is a lithium metal secondary battery utilizing precipitation and dissolution reaction of lithium (Li). However, since in the lithium metal secondary battery, lithium is dendrite-precipitated on the anode and inactivated upon charging, there is a disadvantage that the cycle life thereof is short.
As a battery with the improved cycle life, lithium ion secondary batteries have been commercialized. For the anode of the lithium ion secondary batteries, an anode active material such as a graphite material utilizing intercalation reaction of lithium to the graphite intercalations and a carbonaceous material applying lithium insertion and extraction action to and from the fine pores is used. Therefore, in the lithium ion secondary battery, lithium is not dendrite-precipitated and the cycle life is long. Further, since the graphite material or the carbonaceous material is stable in the air, large merit can be obtained in view of industrial production.
However, for the anode capacity by intercalation, there is the upper limit as defined by composition, C6Li of the first stage graphite intercalation compound. Further, controlling fine pore structure of the carbonaceous material is industrially difficult, and results in decreased specific gravity of the carbonaceous material, and therefore does not act as an effective means for improving anode capacity per unit volume, furthermore improving battery capacity per unit volume. It is known that certain low-temperature fired carbonaceous materials show the anode discharge capacity beyond 1000 mAh/g. However, since such materials have a large capacity at a noble potential of 0.8 V or more in the counter lithium metal, there is a shortcoming that the discharge voltage is decreased when the battery is formed by using a metal oxide or the like for the cathode.
From the foregoing reasons, it is difficult to address the progressive tendency of long time usage of electronic devices and high energy density of the power source with the current carbonaceous materials, and anode active materials with larger lithium insertion and extraction ability is aspired.
Meanwhile, as an anode active material capable of attaining higher capacity, materials obtained by applying the fact that certain lithium alloys are electrochemically and reversibly generated and decomposed have been widely researched. For example, lithium-aluminum alloy has been widely researched, and silicon alloy has been reported in U.S. Pat. No. 4,950,566. However, there is a disadvantage that when such alloys are used for anodes of batteries, cycle characteristics are deteriorated. One of the causes is that such alloys are expanded and shrunk associated with charge and discharge, and pulverized as charge and discharge are repeated.
Therefore, in order to inhibit pulverization of such alloys, for example, it has been considered that substitution is partly made with an element not involved in expansion and shrinkage associated with insertion and extraction of lithium. For example, LiSiaOb (0≦a, 0<b<2) (refer to Japanese Unexamined Patent Application Publication No. H06-325765), LicSi1-dMdOe (M represents a metal element except for alkali metals or a metalloid element except for silicon, 0≦c, 0<d<1, and 0<e<2) (refer to Japanese Unexamined Patent Application Publication No. H07-230800), lithium-silver-tellurium alloy (refer to Japanese Unexamined Patent Application Publication No. H07-288130), and the like have been suggested. Further, a compound containing one or more nonmetallic elements and a metal element or a metalloid element of Group 14 in the long period periodic table (refer to Japanese Unexamined Patent Application Publication No. H11-102705) has been suggested.
However, even in the case using such anode active materials, there is a disadvantage that deterioration of cycle characteristics due to expansion and shrinkage is large, and therefore the batteries with such anode active materials are not sufficient for being used for the mobile devices attaching importance to cycle characteristics.